Linear drive for displacing a component, in particular an aircraft wing component

ABSTRACT

A linear drive for displacing a component, in particular an aircraft wing component, is provided with an input part (1) on the driving side and an output part (4) on the driven side, there being provided between input part (1) and output part (4) an uncoupling device which interrupts a force-locking or a form-locking connection between input part (1) and output part (4) when a predetermined force is exceeded. The input part (1) comprises a freewheel outer part (2) which is connected to the output part (4) via a freewheel inner part (3). Disposed between the freewheel outer part (2) and the freewheel inner part (3) is a tubular freewheel cage (5) with a plurality of pockets (6) which house clamping members (7A, 7B) prestressed by control springs (8) so that they can move in an axial direction. The pockets (6) are provided with inclined ramps (9A, 9B) extending in an axial direction. Spring assembly (10), generating an axial prestress, is disposed between the freewheel inner part (3) and the output part (4).

The invention concerns a linear drive for displacing a component, inparticular an aircraft wing component, according to the type defined inmore detail in the preamble of claim 1.

Linear drives, by which traction and/or pressure forces are linearlytransmitted, are used in various fields. A possible field of use is foraircraft wing components which, when starting or landing, for example,are moved in order to enlarge the lift at low speeds and which enlargethe surface of the hydrofoil and also change the aerodynamics. Crankdrives or linear drives are used for driving said wing components suchas wing flaps. If a blockage now appears in the guide of a wingcomponent, extremely strong forces are generated which have to beabsorbed in the structure of the aircraft. Since the dimension of theaircraft structure is determined by the maximum possible force, theweight also increases therewith.

In designs known in the practice, the force introduced is indirectlylimited by limiting the torque of the power train. But the disadvantageof said limitation is that the force amounts to more than double therequired value due to the kinetics and also to the dispersions ofefficiency.

In WO 90/09921 a driving device having a variable torque-limitationsystem is described. But it is disadvantageous here that in this alreadyknown solution the limitation is relatively inaccurate or distinctdispersions can occur. In addition, the device is relatively deadweight.

Also known in the practice is the limitation of force devices or membersin the power flow which are ruined when a predetermined force isexceeded thus constituting a sort of predetermined breakage point. Butit is, at the same time, a disadvantage that the transmission of forceis terminated therewith and the part must accordingly be repaired beforebeing used again.

Therefore, this invention is based on the problem of providing a lineardrive of the kind mentioned above where the force limitation occurswithout ruining a structural part and where no disadvantageous weightincrease occurs or the structure must be strengthened.

According to the invention, this problem is solved by the stepsmentioned in the characteristic part of claim 1.

In normal operation the force is transmitted from the freewheel outerpart, via the clamping members, to the inner part and then, via thespring assembly, on to the output part. When a predetermined adjustedvalue is exceeded, the spring assembly is compressed so that a relativemovement occurs, between the freewheel outer part and the output part,which produces an uncoupling of the clamping members. An intended andprecise uncoupling of the force transmission is obtained by this devicewithout ruining a structural part.

By an adequate design of the linear freewheel provided in this manner,it can act in both directions, that is, a force limitation can beproduced both in traction and in pressure.

Advantageous additional designs and developments of the invention can beseen from the sub-claims and the embodiments that, in principle, aredescribed herebelow with the aid of the drawings. In the drawings:

FIG. 1 is a longitudinal section through the linear drive according tothe invention;

FIG. 2 is a cross-section through the freewheel cage along line II--IIof FIG. 1;

FIG. 3 is the same section of the linear drive according to FIG. 1 atthe start of actuation;

FIG. 4 is the same section of the linear drive according to FIG. 1 at amaximum run-in position;

FIG. 5 is the linear drive of FIG. 1 at a maximum full position; and

FIG. 6 is a longitudinal section through a linear drive having twospring assemblies.

The linear drive has an input part 1, a freewheel outer part 2, afreewheel inner part 3 and an output part 4 connected therewith. Betweenthe freewheel outer part 2 and the freewheel inner part 3 is a tubularfreewheel cage 5. The freewheel cage 5 is provided with a plurality ofpockets 6 in each of which are housed two clamping members, in the formof spherical rollers 7A and 7B, which are prestressed by a clampingmember control spring 8 situated therebetween. From FIG. 2 it can beseen that, for example, eight pockets 6 with spherical rollers 7A areuniformly distributed on the periphery of the freewheel cage 5. FromFIG. 1 it can be seen that several rows of pockets (three rows in theembodiment) are consecutively disposed in an axial direction, thespherical rollers 7A and 7B in the pocket 6 are separated from eachother, in an axial direction, by the clamping member control spring 8being held under prestress.

From FIG. 1 it can also be seen that the freewheel inner part 3 hasinclined ramps 9A and 9B which likewise extend in an axial direction. Ascan be seen from the figure, ramps 9A and 9B, opposed to one another,one spherical roller 7A and 7B lying as a clamping member on arespective ramp under prestress of the appertaining clamping membercontrol spring 8 are coordinated with each pocket 6.

Instead of the spherical rollers 7A and 7B, other suitable parts canalso be used such as self-aligning rollers, cylindrical rollers or alsoballs. Clamping members with asymmetrical curves or profiles are alsopossible-depending on the specific use.

The force from the input part 1 flows to the outer part 4 via thefreewheel outer part 2, the freewheel cage 5, the freewheel inner part 3and a spring assembly 10. In addition, an outer sleeve 11 is connectedwith the output part 4. Between the outer sleeve 11 and the freewheelouter part 2 is situated a guide device which has several axial grooves12 distributed on the periphery in the outer sleeve 11 and longitudinalribs or longitudinal webs 13, on the outer periphery of the freewheelouter part 2, interact therewith. The guide device also prevents arotation of outer sleeve 11 relative to freewheel outer part 2.

The linear drive according to the invention operates as follows.Departing from the normal position shown in FIG. 1, the force flows fromthe freewheel outer part 2 to the output part 4, via the sphericalrollers 7A as clamping members, and from thereon, via the freewheelinner part 3 and the spring assembly 10. If the movement of the outputpart 4 is now prevented, for example, by icing of a wing flap to bedisplaced, the preset force in the spring assembly 10 is thus exceeded,and the springs of the spring assembly 10 are compressed. In theembodiment, they are moved to the right by the freewheel inner part 3.The distance between the spring assembly 10 and the freewheel cage 5 isenlarged in an axial direction (see start of actuation in FIG. 3). Withincreasing excessive force and therewith increasing displacement of thefreewheel inner part 3 relative to the freewheel outer part 2, the usedspherical rollers 7A are pushed down to the left in the embodiment, bythe front walls of the pockets 6 along their ramps 9A and against theprestress of the clamping member control springs 8. In this manner, thespherical rollers become free, the flow of force is interrupted, and thedesired freewheel is generated.

A maximum run-in position is shown in FIG. 4.

However, the linear drive shown also operates in a reverse direction,that is, with the power flow from the right to the left or from theoutput part 4 in a direction toward the input part 1. While in the abovedescribed power flow from the left to the right, the flow takes place,via a stop ring 15, which abuts against a stop of the freewheel innerpart 3, the power flow now goes, via a stop ring 14, which abuts againsta stop nut 16 screwed on a front side of the freewheel inner part 3.When a preselected force is exceeded, the spring assembly 10 is, inturn, pressed together by the stop nut 16. If, at the same time, ablockage, in turn occurs, the stop nut 16 compresses the springassembly. The outer sleeve 11, which is firmly connected with the outputpart 4, here remains stationary. The outer sleeve 11 has a tubular stopshoulder 17 against which the freewheel cage 5 strikes during thedisplacement. During the further movement, in this manner, the sphericalrollers 7B become disengaged, for they are drawn down to the right alongtheir respective inclined ramps 9B. In this manner, the desiredfreewheel is also obtained for this power flow.

However, in order to again attain in the respective end positions aresetting or return to the normal position, a special device must beprovided, for in the end positions the spherical rollers 7A and 7B, whenseeking a return, would otherwise immediately get in gear again asclamping members so that no return to the normal position would bepossible anymore.

A spring device is provided for this purpose where the spring iscentered and holds the freewheel cage in its normal position or bringsit back to said position.

The spring device has an outer ring 18 with an inwardly projecting ringnose 19 and an inner ring 20 with an outwardly projecting ring nose 21which engages a rear of the ring nose 19. A control spring 22 isstretched between a front wall 23 and a stop ring 24. The stop ring 24abuts, under prestress by the control spring 22, against a front-sidecollar 25 of a bolt 26 and can be pressed on a tubular front stop of thefreewheel cage 5 by an intermediate ring 27. A snap ring 36 forms afastening for the outer ring 18 on the side remote from the freewheelcage 5.

As can be seen from FIG. 5, the inner ring 20 is spaced from the inputpart 1 or at a distance therefrom. In this position, the inner ring 20must first be returned by the control spring 22 to a front-side stop onthe input part 1. In this manner, the freewheel cage 5 is then againcentered with its clamping members.

In the maximum run-in position of FIG. 4, the outer ring 18 has movedfrom the ring nose 21 of the inner ring 20. In this case, the freewheelcage 5 is again centered to the right by the control spring 22 untilreaching the normal position.

This means that unlike the prior art wherein, for example, breakingpoints exist, multiple points can optionally be tried out whether or nota blockage still exists, therefore no breakage or deformation of theparts occur here.

In the solution according to the invention, a clear travel or a cleardisplacement, which must be limited only for reasons of needed space, isobtained in the case of an overload. This clear displacement can thusalso be used for measuring the displacement path by adequate errordetectors. Thus, for example, a release of the force limitation or ofthe uncoupling device outward by means of an adjustable valve 29 can beindicated and additionally optionally signaled by control members. Thisdevice is shown only in principle in FIG. 1. It is thus possible, forexample, to provide for a slide rod 30, which is connected with thefreewheel inner part 3 and, upon displacement of the freewheel innerpart 3, moves the valve 29 in the direction of arrow 31. In this manner,it is possible, in a linear drive which actuates several components, todetect in which component the force was exceeded.

By means of said indicator device, or by any other device, it is alsopossible to give notice in the sense that a disconnecting device for thedrive has been actuated by corresponding control members.

In FIG. 6, a development of the above described embodiment is shown. Thelinear drive in this figure operates basically in the same way,wherefore the same reference numerals have been used and the manner ofoperation has not been discussed in detail herebelow.

The only difference from the above described embodiments is that twospring assemblies 10A and 10B have been provided which have differentspring prestresses. During power flow from the right to the left, bothspring assemblies 10A and 10B are connected in parallel. The connectionof the spring assemblies in series is here weaker than the connection inparallel whereby an asymmetric characteristic line is obtained in bothdirections of power flow. The causes of said different characteristiclines are, besides the stop rings 14 and 15, two added thrust rings 32and 33 which are provided and lie between both spring assemblies 10A and10B. The thrust ring 33 here abuts, under spring prestress, against anannular recess 35 of the freewheel inner part while the stop ring 32abuts against an annular recess 34 of the output part 4.

The freewheel outer part 2, the freewheel inner part 3 and the freewheelcage 5 are, in general, designed with a circular cross-section. Butother cross-sectional shapes, such as a polygonal cross-section, arealso evidently possible. Likewise, the inclined ramps 9A and 9B aregenerally provided in the freewheel inner part, but within the scope ofthe invention an inverse arrangement is also possible, that is, that theramps can be situated on the freewheel outer part.

Reference numerals

    ______________________________________                                        Reference numerals                                                            ______________________________________                                         1    input part       18    outer ring                                        2    freewheel outer part                                                                           19    ring nose                                         3    freewheel inner part                                                                           20    inner ring                                        4    output part      21    ring nose                                         5    freewheel cage   22    control spring                                    6    pockets          23    front wall                                        7    spherical rollers                                                                              24    stop ring                                         8    clamping member control                                                                        25    front-side collar                                      spring           26    bolt                                              9    inclined ramps   27    intermediate ring                                10    spring assembly  28    front stop                                       11    outer sleeve     29    adjustable valve                                 12    axial grooves    30    slide rod                                        13    longitudinal ribs                                                                              31    arrow direction                                        or webs          32    additional thrust rings                          14    stop ring        33    additional thrust rings                          15    stop ring        34    annular recess                                   16    stop nut         35    annular recess                                   17    stop shoulder    36    snap ring                                        ______________________________________                                    

I claim:
 1. A linear drive for displacing a component, in particular anaircraft wing component, comprising an input part driving an outputpart; an uncoupling device being provided between said input part andsaid output part which interrupts a connection between said input partand said output part when a predetermined force is exceeded;wherein saidinput part has a freewheel outer part which is connected, via afreewheel inner part, with said output part; a tubular freewheel cage issituated between said freewheel outer part and said freewheel innerpart, said tubular freewheel cage has a plurality of pockets which houseclamping members prestressed by control springs so that they can move inan axial direction; and a pair of inclined ramps are coordinated witheach pocket situated along said tubular freewheel cage; and at least onespring assembly is disposed between said freewheel inner part and saidoutput part for generating an axial prestress.
 2. A linear driveaccording to claim 1, wherein said connection is a force-lockingconnection.
 3. A linear drive according to claim 1, wherein saidconnection is a form-locking connection.
 4. A linear drive according toclaim 1, wherein said freewheel cage is centered in a central positionby at spring device.
 5. A linear drive according to claim 4, whereineach pocket is provided with said inclined ramps disposed axiallyhomologous to each other.
 6. A linear drive according to claim 5,wherein said clamping members are selected from a group consisting ofspherical rollers, cylindrical rollers and self-aligning rollers.
 7. Alinear drive according to claim 5, wherein said clamping members areballs.
 8. A linear drive according to claim 7, wherein a guide device isdisposed between said freewheel outer part and said output part.
 9. Alinear drive according to claim 7, wherein a guide device is disposedbetween said freewheel outer part and a part connected with said outputpart.
 10. A linear drive according to claim 8, wherein said guide devicecomprise axial grooves with longitudinal ribs located therein.
 11. Alinear drive according to claim 10, wherein two spring assemblies, eachhaving different spring prestresses, are provided and disposed so as toyield different prestresses relative to one of pressure and traction.12. A linear drive according to claim 11, wherein the displacementbetween said freewheel outer part and said freewheel inner part isdetectable and can be indicated by an error detector.
 13. A linear driveaccording to claim 12, wherein a disconnectin vice is provided for saidlinear drive.
 14. A linear drive according to claim 9, wherein saidguide device comprises axial grooves with longitudinal ribs locatedtherein.
 15. A linear drive according to claim 14, wherein two springassemblies, each having different spring prestresses, are provided anddisposed so as to yield different prestresses relative to one ofpressure and traction.
 16. A linear drive according to claim 15, whereinthe displacement between said freewheel outer part and said freewheelinner part is detectable and can be indicated by an error detector. 17.A linear drive according to claim 16, wherein a disconnecting device isprovided for said linear drive.